Radio system and method



Sept. 13, 1932. UE 1,876,694

RADIO SYSTEM AND METHOD Filed May 21, 1928 INVENTOR gzaffi'zg d KruawMiG/Bani,

A TTORNE YS Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE GEOFFREYGOTTLIEB KRUESI,OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELEGRAPHCOMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALI- ronnmApplication filed May 21,

This invention relates generally to systems and methods of effectingtransmission of radio energy between two or more stations. It hasparticular application to radio signaling systems utilizing directionalradio antennae.

It is an object of this invention to make radio signaling systems morereliable. and uniform inv operation, and to render them immune fromfading effects.

Briefly, the above object is attained by utilizing for the transmissionof radio signals that component of the transmitted signal which followsthe surface of the earth (com monly termed the ground wave) to theexclusion of the high angle radiation, and re ducing the attenuation ofthe ground wave by transmitting a wave having both horizontally andvertically polarized components.

Referring to the drawing:

Figure 1 illustrates diagrammatically a plan view of a radio networkincorporating the principles of this invention.

Fig. 2 is a side elevational view illustrating diagrammatically atransmitting apparatus for producing ground waves.

3 is a front view of the apparatus shown in Fig. 2. I r

Fig. 4 is a diagram illustrating schematica'lly transmitting andreceiving apparatus for one of the stations of the network shown in Fig.1.

Experiments have indicated that the energy radiated from the usualantenna divides into two parts, one of'which iscommonly termed theground wave and which spreads out horizontally from the source ofradiation and is propagated immediately above the surface of the ground,while, the other consists of radiations which are reflected upward fromthe earths surface toward the Heavyside layer. In ordinary radiosystems, communication is eflected by the energy of the reflected waves,:that is waves which at the transmitted end are directed upward from theground surface toward the Heavyside layer and which are probablyreflected one or more times from'the Heavyside layer before beingreceived. It is a commonly accepted fact that with the usual present dayradio systems, reception is not al- 'RAIIO SYSTEM AND METHOD 1928.Serial No. 279,293.

pheric conditions. The ground waves which are sent out from the presentday transmitting antennae, generally die out within the short distanceof from 10 to 20 miles, and therefore are not received unless thereceiving station happens to be comparatively close to the transmittingstation.

As disclosed in-copending application No. 279,244L filed in the jointnames of Kolster and Kruesi, which is assigned to the assignee of thisapplication, is it possible to concentrate radio waves in the form of atrue beam by the proper use of a paraboloidal reflector. I have made thediscovery that radio ground waves, which were previously considered tobe of little value for radio communication between remote points, can betransmitted con siderable distances by utilizing a paraboloidalreflector to concentrate substantially all the radiated energy along thesurface of the ground. I have also found that when prop erly polarized,the concentrated radio waves follow the surface of the ground and arenot reflected toward the Heavyside layer to any extent. 7

In Fig. 2 of the drawing I. have shown diagrammatically a transmittingapparatus somewhat similar to that shown in the above copendingapplication. This apparatus'consists of aparaboloidal reflecting surface10 made of conducting material such as sheet copper, andhaving anantenna radiator 11 placed at its focal center. The radiator in thiscase consists of crossed antenna conductors 12 and 13, which have theirmidpoints coupled to a suitable signaling circuit 14. With such anapparatus, assuming that the signaling. circuit 14 supplies oscillatoryenergy of the. proper frequency to the radiator 11, which preferably isof a frequency four times the focal length of the reflector, atrue beamof electromagnetic radiation is project'ed from the reflector. If theradiator 11 consists of a single conductor arranged in avertical plane,then the polarization ofithe I IOU of a single conductor in a horizontalplane, the polarization is horizontal. By utilizing t-wo conductors 12and 13 extending in different planes, one in this case being horizontaland the other vertical, the transmitted wave consists of bothhorizontally and vertically polarized components. By directing the axisof the reflector along the surface of the ground, the radiated waves canbe propagated parallel to the ground surface so as to transmit intenseground waves in any desired direction.

In order that the ground waves may effectively be transmittedcomparatively great distances, the radiation field should have ahorizontal" component, as vertically polarized waves are quicklyabsorbed by the ground. However a certain vertical component is to bedesired. Therefore for the method of my invention, I prefer-to employapparatus such as that described above which propagates waves having ahorizontally polarized component and at least appreciable vertically)olarized component.

As has been previously explained, with the apparatus described, groundwaves of great intensity may be propagated for comparatively greatdistances and they can be readily received at distances of from 200 to500 miles from the transmitter. Such ground waves are entirelyindependent of conditions of the Hea-vyside layer, and thereforecontinuous and reliable communication can be had between a transmittingand receiving station, irrespective of changing climaticeonditions,without experiencing fading effects.

At thereceiving station I prefer to employ apparatus somewhat similar tothe transmitting apparatus shown'in Fig. 2. In other words I prefer toemploy a paraboloidal refiector having antenna means positioned adjacentits focal center. No particular form of antenna means is essentialexcept that it should be constructed so as to receive verticallypolarized waves. A receiving apparatus utilizing a paraboloidalreflector with its axis horizontal is desirable since the reflectortends to shield the antenna means from interfering waves reflected downfrom the Heavyside layer.

In Fig. 1 I have shown a complete network utilizing the method describedabove. As theground waves which I employ will not carry over' greatdistances such as are now covered by radio systems, I preferably utilizea network consisting of a number of relay stations which receive andretransmit ground waves. For example I have shown a network consistingof spaced stations A, B, C, D, E, and F, which are each locatedsufiiciently close together, say from 300 to 400 miles apart, so thatany one station can receive ground waves from a preceding or succeedingstation. Assuming that only one way transmission is to be efiectedthroughout this network, each station is provided with a ground wavereceiving and transmitting apparatus, and signals received upon groundwaves may be retransmitted upon ground waves.

A diagrammatic arrangement of apparatus for such a relay station isshown in Fig. l. Thus I have shown a reflector type of receivingapparatus 1 capable of receiving ground waves such as I employ in themethod of this invention, and having its antenna means coupled to asuitable receiver 16. Signal energy detected by this receiver is appliedto a local translator 17. A transmitting apparatus 2 similar to thatpreviously described is also provided, and issupplied with energy from asuitable signaling circuit consisting for example of the oscillator 18,modulator l9, and power amplifier 20. A connection is shown directlybetween the receiver 16 and modulator 19, so that signals maybe directlyrelayed and retransmitted upon ground waves.

It will be apparent that while the method of this invention will notpermit direct transmis ion of signals between two stations locatedextreme distances apart as with other radio systems, it will makepossible systematic radio networks which will operate as reliable aspresent day wire networks.

I claim: l

1. The method of signaling over long distances by radio signal energycomprising generating radio waves atone station, concentrat'ing'saidwaves in one direction substantially entirely in the form of groundwaves, receiving energy of. said'ground waves at a remote point,relaying the received signal energy byjretransmitting ground wavessimilar to said first ground waves, and receiving energy of saidretransmitted waves at re mote station. 2. Aradio'communication systemcomprismg a transmitting anda receiving station, a paraboloidalreflector having its axis sub stantially tangent to the earths surfacewith radiating. means mounted therein having both a horizontal andvertical component at the-transmitter, anda paraboloidal reflector atthe receiver having its axis substantially tangent to the earths surfaceand having therein as the sole essential absorbing ele ment, a conductorlying in a vertical plane intersecting the transmitter and receivingstations.

In testimony whereof,I have hereunto set my hand. i

' GEOFFREY G T LIEB KaUEs

